When running back Zach Bauman picked up a fourth-down fumble and ran it into the end zone from six yards out with just 1:11 to play, it appeared the Cardinals would win their second straight preseason game.

But it wasn't to be, as rookie quarterback Teddy Bridgewater marched the Minnesota Vikings down the field on a seven-play, 83-yard touchdown drive capped off by a 2-yard TD pass to Rodney Smith with :18 left. The Vikings would hold on for a 30-28 win.

Of course teams want to win every game they play, but an 'L' in the preseason is taken with a grain of salt. More important are the reasons why the team lost.

Bridgewater and starter Matt Cassel were sacked only once in 37 dropbacks and combined to throw for 322 yards and three touchdowns in the win.

But Keim says the issues weren't just on the defensive side of the ball.

"Offensively, I thought we pounded the ball pretty good, but we're still not showing the ability to have explosive runs," he said.

Against Minnesota, Cardinal running backs combined to carry the ball 30 times for 65 yards -- a paltry 2.17 yards per carry. It wasn't much better in the win over Houston last week when Arizona backs toted the pigskin 31 times for 74 yards - or 2.39 yards per attempt. Their longest run through two games has been Bauman's 13-yarder in the fourth quarter of the win over the Texans.

As much as there is concern, there are also reasons for it, according to Keim.

"How physical can you be in camp anymore," he asked. "And the ability for your offensive line to play in unison when you're talking about combination blocks to the second level, your timing.

"And quite frankly, our explosive runner is Andre Ellington. Andre didn't play a whole lot, he played just enough to get his pads soiled."

Ellington's small preseason workload wasn't unexpected. In two games, he's played a total of 19 snaps, carrying four times for 12 yards. The second-year back will be featured much more prominently in the 2014 regular season.

There could be help on the way in the form of veteran center Lyle Sendlein, who has missed a good portion of camp with a calf injury.

"Lyle looks great, we're going to test him out (Monday) and there some expectations that we could have Lyle back as soon as Wednesday," Keim said.

The Cardinals continue their preseason schedule Sunday night when they host the Cincinnati Bengals at University of Phoenix Stadium in game that will be nationally televised by NBC.